Trenched shield gate power semiconductor devices and methods of manufacture

Abstract

A semiconductor power device includes a drift region of a first conductivity type, a well region extending above the drift region and having a second conductivity type opposite the first conductivity type, an active trench extending through the well region and into the drift region. The active trench, which includes sidewalls and bottom lined with dielectric material, is substantially filled with a first conductive layer and a second conductive layer. The second conductive layer forms a gate electrode and is disposed above the first conductive layer and is separated from the first conductive layer by an inter-electrode dielectric material. The device also includes source regions having the first conductivity type formed inside the well region and adjacent the active trench and a charge control trench that extends deeper into the drift region than the active trench and is substantially filled with material to allow for vertical charge control in the drift region. The charge control trench can be lined with a layer of dielectric material and substantially filled with conductive material. The active trench can include a second shield electrode made of conductive material disposed below the first shield electrode. The first conductive layer inside the active trench can form a secondary gate electrode that is configured to be electrically biased to a desired potential. The semiconductor device can also include a Schottky structure formed between the charge control trench and a second adjacent charge control trench.

1. A semiconductor device comprising:
 a drift region of a first conductivity type; 
 a well region extending above the drift region and having a second conductivity type opposite the first conductivity type; 
 an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material; 
 source regions having the first conductivity type formed in the well region adjacent the active trench; 
 a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region; 
 wherein the charge control trench is lined with a layer of dielectric material and substantially filled with conductive material; and 
 wherein the active trench further comprises a third conductive layer disposed below the first conductive layer, the third conductive layer is smaller than the first conductive layer. 
 
     
     
       2. A semiconductor device comprising:
 a drift region of a first conductivity type; 
 a well region extending above the drift region and having a second conductivity type opposite the first conductivity type; 
 an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material, the first conductive layer forming a first shield electrode; 
 source regions having the first conductivity type formed in the well region adjacent the active trench; 
 a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region; and 
 wherein the active trench further comprises a second shield electrode made of conductive material disposed below the first shield electrode, the second shield electrode is smaller than the first shield electrode. 
 
     
     
       3. The semiconductor device of  claim 2  wherein the first and second shield electrodes vary in thickness. 
     
     
       4. The semiconductor device of  claim 2  wherein the first and second shield electrodes are configured to be independently biased. 
     
     
       5. A semiconductor device comprising:
 a drift region of a first conductivity type; 
 a well region extending above the drift region and having a second conductivity type opposite the first conductivity type; 
 an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material; 
 source regions having the first conductivity type formed in the well region adjacent the active trench; 
 a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region; 
 wherein the charge control trench is substantially filled with dielectric material; and 
 wherein the active trench further comprises a third conductive layer disposed below the first conductive layer, the third conductive layer is smaller than the first conductive layer. 
 
     
     
       6. The semiconductor device of  claim 5  further comprising a lining of second conductivity material extending along exterior sidewalls of the charge control trench. 
     
     
       7. A semiconductor device comprising:
 a drift region of a first conductivity type; 
 a well region extending above the drift region and having a second conductivity type opposite the first conductivity type; 
 an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material; 
 source regions having the first conductivity type formed in the well region adjacent the active trench; 
 a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region; and 
 a Schottky structure formed between the charge control trench and a second adjacent charge control trench. 
 
     
     
       8. A semiconductor device comprising:
 a drift region of a first conductivity type; 
 a well region extending above the drift region and having a second conductivity type opposite the first conductivity type; 
 an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material; 
 source regions having the first conductivity type formed in the well region adjacent the active trench; 
 a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region; 
 wherein the first conductive layer inside the active trench forms a secondary gate electrode that is configured to be electrically biased to a desired potential; and 
 wherein the active trench further comprises a third conductive layer disposed below the first conductive layer, the third conductive layer is smaller than the first conductive layer. 
 
     
     
       9. The semiconductor device of  claim 8  wherein the gate electrode and the secondary gate electrode are configured to be independently electrically biased. 
     
     
       10. The semiconductor device of  claim 9  wherein the secondary gate electrode is configured to be biased at a constant potential at approximately the threshold voltage of the semiconductor device. 
     
     
       11. The semiconductor device of  claim 9  wherein the secondary gate electrode is configured to be biased at a potential that is greater than a potential applied to the source regions. 
     
     
       12. The semiconductor device of  claim 9  wherein the secondary gate electrode is configured to be coupled to a potential at approximately the threshold voltage of the semiconductor device before a switching event. 
     
     
       13. The semiconductor device of  claim 8  wherein the charge control trench is lined with a layer of dielectric material and substantially filled with conductive material. 
     
     
       14. The semiconductor device of  claim 13  wherein a source electrode is configured to couple the conductive material inside the charge control trench to the source region. 
     
     
       15. The semiconductor device of  claim 8  wherein inside the charge control trench is disposed a plurality of conductive layers stacked vertically and separated from each other and from the trench sidewalls by dielectric material. 
     
     
       16. The semiconductor device of  claim 15  wherein the plurality of conductive layers inside the charge control trench are configured to be electrically biased to provide vertical charge balancing in the substrate. 
     
     
       17. The semiconductor device of  claim 16  wherein the plurality of conductive layers inside the charge control trench are configured to be independently biased. 
     
     
       18. The semiconductor device of  claim 15  wherein sizes of the plurality of conductive layers inside the charge control trench vary. 
     
     
       19. The semiconductor device of  claim 18  wherein the size of a first conductive layer deeper inside the charge control trench is smaller than the size of a second conductive layer that is disposed above the first conductive layer. 
     
     
       20. The semiconductor device of  claim 8  wherein the charge control trench is substantially filed with dielectric material. 
     
     
       21. The semiconductor device of  claim 20  further comprising a lining of second conductivity material extending along exterior sidewalls of the charge control trench. 
     
     
       22. A semiconductor device comprising
 a drift region of a first conductivity type; 
 a well region extending above the drift region and having a second conductivity type opposite the first conductivity type; 
 an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material; 
 source regions having the first conductivity type formed in the well region adjacent the active trench; 
 a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region; and 
 a Schottky structure formed between the charge control trench and a second adjacent charge control trench; 
 wherein the first conductive layer inside the active trench forms a secondary gate electrode that is configured to be electrically biased to a desired potential. 
 
     
     
       23. The semiconductor device of  claim 8  wherein the third conductive layer is isolated from the secondary gate electrode and the trench sidewalls and bottom by dielectric material, the third conductive layer forming a shield electrode that is configured to be electrically biased to a desired potential.